Recently, solid-state camera devices are built in many video cameras and electronic still cameras in order to reduce size and weight of such cameras. As shown in FIG. 6, a solid-state camera device, generally, comprises a plurality of sets of a light-receiving part 1 and a vertical transfer part 6 which are arranged along by each other on a semi-conductor substrate 7, a plurality of vertical transfer electrodes 5 which are formed on each of the vertical transfer parts 6, a shading film 4 which covers the vertical transfer parts 6 and opens on the light-receiving parts 1, and a plurality of color filters 3 which are arranged above each of the light-receiving parts 1 and, further comprises, in order to focus the incident light effectively on the light-receiving parts, a plurality of generally hemispherical microlenses 2 as a light-focusing part formed above each of the color filters 3 at positions corresponding to the light-receiving parts 1. A process of forming the microlens 2 is as follows. First, a transparent film of a composition for the microlens having photo-sensitivity and thermoplasticity is formed by applying the composition on the substrate 7 on which the shading film 4 and the color filter 3 have been arranged. Next, the film is patterned by exposure with a specified mask and development. Then, the patterned film is softened by heat treatment to make the patterns generally hemispherical.
As shown in FIG. 7(a), in the case where an eye point distance (distance between the shading film 4 and an aperture stop 9 defining an exit pupil 9a) L in an optical system of a camera is relatively long (L=L1), an incident light IL, which has passed through the microlens 2, can enter into an opening 4a of the shading film 4 (i.e., the light-receiving part 1) not only in the middle of the camera region 21 (a region in the front of the exit pupil) but region in the peripheral camera region 22 (a region remote from the middle of the camera region along the substrate surface).
On the other hand, in the case where an eye point distance L is relatively short (L=L2) as shown in FIG. 7(b), in the peripheral camera region 22, particularly in the peripheral region in the lateral direction, an incident angle of IL to the microlens becomes larger compared to the case where an eye point distance is long (L=L1), and a part of IL is prevented from entering into the opening 4a (i.e., so-called “eclipse” of the incident light IL occurs), consequently, a proportion of a light quantity that enters into the light-receiving part 1 decreases. Thus, sensitivity of the camera device becomes lower in the peripheral camera region 22 than in the middle of the camera region 21, resulting in a phenomenon that brightness diminishes in the peripheral region of its screen (so-called deterioration of “shading”). A broken line in FIG. 8 shows an output voltage wave in one laterally scanning period 1H of a camera, indicating that the intensity of the output signal in the peripheral camera region Ve is significantly lower than the signal intensity in the middle of the camera region V0.
As a method of preventing the deterioration of the shading, JP-A 140609/1994 describes a technique of performing slight-scaling with referring to the center of a camera region as shown in FIG. 9. The “slight-scaling” is a technique of shifting each of the microlenses 2 gradually larger toward the center of the camera region based on the corresponding light-receiving parts 1, as the location of the microlens is getting closer to the peripheral camera region 22 from the middle of the camera region 21 by using an interval P′ for a microlens array (consisting of microlenses 2 having a common size) which is smaller than an interval P for the light-receiving parts 1, i.e., opening 4a (P′=a×P; scale a is <1, e.g., “a” is set to be 0.9999). Thus, the eclipse of the incident light IL in the peripheral camera region 22 is reduced. A dotted line in FIG. 8 indicates that the slight-scaling technique decreased the difference between Ve and V0, that is, the shading was somewhat corrected in comparison with the case where the slight-scaling was not performed (the broken line).
Further, in an optical system of a camera, especially when its aperture stop opens fully, a phenomenon occurs that a quantity of the light having passed through near the rim of its lens is less than that of the light having passed through the middle of the lens (so-called “rim darkening”). The slight-scaling technique can not sufficiently correct the shading caused by the rim darkening.
Therefore, an object of the present invention is to provide a solid-state camera device which can correct the shading caused by the eclipse of the incident light and, further can correct the shading caused by the rim darkening, and to provide a method of manufacturing it. Another object of the present invention is to provide a method of manufacturing a mask for forming light-focusing parts of such a solid-state camera device.
These objects as well as other objects and advantages of the present invention will become apparent to those skilled in the art by the following description with reference to the attached drawings.